According to a study by the American Board of Surgery and the Association of Program Directors in Surgery, a graduating general surgeon should be competent to perform 121 “Level-A” procedures after a 5 year residency program. The same study shows the level of experience in these procedures for the 2005 graduating class of surgeons. The study found that for sixty-three (63) procedures, the mode (most commonly reported) experience was 0. In addition, there was significant variation between residents in operative experience for specific procedures. The study expresses concern about the adequacy of training of general surgeons in the United States and concludes that there is a need for methods to be developed to allow surgeons to reach a basic level of competence in less common procedures and also objective means to determine competency in the commonly performed procedures.
Many surgical techniques require dexterous movement and control by the surgeon. This dexterity cannot be developed by reading textbooks or watching instructional videos. Animal models or cadavers have been the default method for hands-on surgical training in the past, but they are costly, not readily available and may pose biohazard issues. Systems of computerized virtual reality or electromechanical devices may be useful and effective but their cost restricts their reach and thus their impact in the broader medical community. For training purposes, it is desired that the model stay as consistent and repeatable as possible, is readily available, and can be mass produced and distributed. In the field of ophthalmic surgery, there are several examples of creating a cataract surgery model in the prior art. However, some are over-simplified, such as U.S. Pat. No. 8,235,728 by Stoll, which describes a technique which may not be repeatable. Other methods are based on animal tissue, thus subject to inter and intra-species variability, high cost and availability see U.S. Pat. No. 6,887,083. Other methods like those described by Maloney U.S. Pat. No. 4,762,495, Radow in U.S. Pat. No. 5,893,719 and Carda U.S. Pat. Nos. 8,137,111 and 8,128,412 rely on the assembly of multiple parts and requires multiple manufacturing steps and tools to create a surgical model. U.S. Pat. No. 7,272,766 shows a method for forming tissue analogs.
3D Printing
Additive manufacturing, known conventionally as 3D Printing (3DP), rapid prototyping (RP), Direct Digital Manufacturing (DDM), is the generic term used for technologies that use a layering process to build three-dimensional objects. In contrast to subtractive manufacturing, such as CNC machining, additive manufacturing achieves the desired form by depositing material in successive layers, as described in U.S. Pat. No. 7,896,639. The layer deposition is completely automated and control is derived from digital surface mesh files (.STL). These surface files can be generated by CAD (Computer Aided Design) software or obtained from medical imaging data such as CT or MRI with segmenting software.
A significant advantage of additive manufacturing is the possibility of printing different parts at once in a single “build”. A build is a term used in the art of 3D printing to identify the end result of the printing process. This can be a single part, an array of identical parts, an array of different parts, and even an assembly of parts; this results in part assemblies without requiring any assembly process. No subtractive manufacturing method is capable of producing this level of complexity from a single process. A device with multiple components is usually assembled in a secondary operation from individual parts joined together by fasteners, glues, snaps, and the like.
Very recent advances in 3D printing technology allow for the creation of builds with discrete regions having customized mechanical properties. In other words, it is possible to print a single build that contains hard components or regions, soft components or regions, and components and regions with properties in-between. This is achieved by the simultaneous deposition of two complementary materials, one soft and one hard, in controlled proportions, in specific 3D coordinates. Similar to the way an office inkjet printer combines a discrete number of colors in the cartridge to create any color pixel on paper, a multi-material 3D printer combines materials to create any intermediate material on a voxel (3D pixel) of the build. The technology currently used to do this is based on what is known as “Polyjet” and is described in U.S. Pat. Nos. 6,569,373 and 7,300,619 from Napedensky and U.S. Pat. No. 7,225,045 from Gothait. Using multi-material 3D printing technology, one can print an assembly of multiple sub-structures, and each sub-structure can have a specific material property assigned to it. This was used by Parsi for the fabrication of hearing aids, as disclosed in U.S. Pat. No. 7,875,232. An example application of a surgical model of a flexible vessel made with rapid prototyping is shown in U.S. Pat. Pub. No. US2011/0060446 and U.S. Pat. Pub. No. US2010/0209899A1 and simulated abdominal wall in layers are shown in U.S. Pat. Pub. No. 2010/0209899.